package com.ruoyi.common.qy.utils;

import java.util.Date;

public class SnowflakeIdGenerator {
    // 起始的时间戳（2024-01-01 00:00:00）
    private final static long START_TIMESTAMP = 1704067200000L;

    // 每一部分占用的位数
    private final static long SEQUENCE_BIT = 12;   // 序列号占用的位数
    private final static long MACHINE_BIT = 5;     // 机器标识占用的位数
    private final static long DATACENTER_BIT = 5;  // 数据中心占用的位数

    // 每一部分的最大值
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    // 每一部分向左的位移
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTAMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    private long datacenterId;  // 数据中心
    private long machineId;     // 机器标识
    private long sequence = 0L; // 序列号
    private long lastTimestamp = -1L; // 上一次时间戳

    public SnowflakeIdGenerator(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than " + MAX_DATACENTER_NUM + " or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    public synchronized long nextId() {
        long timestamp = System.currentTimeMillis();

        if (timestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards. Refusing to generate id");
        }

        if (timestamp == lastTimestamp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;

        return ((timestamp - START_TIMESTAMP) << TIMESTAMP_LEFT)
                | (datacenterId << DATACENTER_LEFT)
                | (machineId << MACHINE_LEFT)
                | sequence;
    }

    private long tilNextMillis(long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }

    // 解析雪花ID
    public static void parseId(long id) {
        long timestamp = (id >> TIMESTAMP_LEFT) + START_TIMESTAMP;
        long datacenterId = (id >> DATACENTER_LEFT) & MAX_DATACENTER_NUM;
        long machineId = (id >> MACHINE_LEFT) & MAX_MACHINE_NUM;
        long sequence = id & MAX_SEQUENCE;

        System.out.println("雪花ID解析结果:");
        System.out.println("ID: " + id);
        System.out.println("时间戳: " + timestamp + " -> " + new Date(timestamp));
        System.out.println("数据中心: " + datacenterId);
        System.out.println("机器ID: " + machineId);
        System.out.println("序列号: " + sequence);


    }

    public static void main(String[] args) {
        SnowflakeIdGenerator idGenerator = new SnowflakeIdGenerator(1, 1);

        for (int i = 0; i < 10; i++) {
            long id = idGenerator.nextId();
            System.out.println("生成的ID: " + id);
            parseId(id);
            System.out.println("--------------------");
        }
    }
}
